Suction cover assembly for reciprocating pumps

ABSTRACT

A suction cover nut for a reciprocating pump includes a body configured to be at least partially received within an access port of a fluid cylinder of the reciprocating pump. The body extends a length along a central longitudinal axis. The body includes a thread configured to threadably connect the suction cover nut to the fluid cylinder within the access port. The thread extends along the central longitudinal axis of the body. The body includes a recess configured to receive a suction cover of the reciprocating pump therein. The recess is tapered inwardly along the central longitudinal axis of the body.

CROSS-REFERENCE TO RELATED APPLICATION

This Application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 62/553,298, filed on Sep. 1, 2017 and entitled “FLUID END RETAINER NUT AND SUCTION COVER RETENTION,” which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to reciprocating pumps, and, in particular, to suction cover assemblies used in reciprocating pumps.

BACKGROUND OF THE DISCLOSURE

In oilfield operations, reciprocating pumps are used for different applications such as fracturing subterranean formations to drill for oil or natural gas, cementing the wellbore, or treating the wellbore and/or formation. A reciprocating pump designed for fracturing operations is sometimes referred to as a “frac pump.” A reciprocating pump typically includes a power end and a fluid end (sometimes referred to as a cylindrical section). The fluid end can be formed of a one piece construction or a series of blocks secured together by rods. The fluid end includes a fluid cylinder having an opening for receiving a plunger or plunger throw, an inlet valve, an outlet valve, and an access port. Reciprocating pumps are oftentimes operated at pressures of 10,000 pounds per square inch (psi) and upward to 25,000 psi and at rates of up to 1,000 strokes per minute or even higher during fracturing operations.

The access port of reciprocating pumps is used to service the plunger and inlet and outlet valves of the reciprocating pump, for example during field use where rapid maintenance and/or replacement may be important for the profitability of a well service operation. In the fluid cylinder of a reciprocating pump, the access port may be closed using a suction cover that is held in place with a suction cover nut that is threadably connected to the fluid cylinder, for example using buttress threads. But, despite the selection of relatively strong materials and the use of double shot peening and/or other hardening techniques, the relatively high cyclical loads on the suction cover may cause the threads to fatigue and ultimately fail. For example, the relatively high cyclical loads exerted on the suction cover nut during cyclical pumping of the reciprocating pump may impart an unequal load distribution along the axial length of the threads. Failure of the threaded connection between the suction cover nut and the fluid cylinder may cause the reciprocating pump to leak at the access port (e.g., the suction cover nut may weep well service fluid to the atmosphere through the threads) and/or may necessitate costly replacement of the suction cover nut and/or the fluid cylinder.

With the recent advances in longer lasting fluid cylinders (e.g., Duralast® SS Fluid Cylinders), the failure point of the threaded connection between the suction cover nut and the fluid cylinder is becoming a bigger issue, for example as compared to the typical cracking of the fluid cylinder at the crossbores due to the high cyclical fatigue forces of reciprocating pumps.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter. Nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In a first aspect, a suction cover nut for a reciprocating pump includes a body configured to be at least partially received within an access port of a fluid cylinder of the reciprocating pump. The body extends a length along a central longitudinal axis. The body includes a thread configured to threadably connect the suction cover nut to the fluid cylinder within the access port. The thread extends along the central longitudinal axis of the body. The body includes a recess configured to receive a suction cover of the reciprocating pump therein. The recess is tapered inwardly along the central longitudinal axis of the body.

In one embodiment, the recess includes a sidewall that is configured to transfer axial forces acting during operation of the reciprocating pump radially outward relative to the central longitudinal axis.

In some embodiments, the body extends the length along the central longitudinal axis from an exterior end portion to an interior end portion. The recess extends a depth into the interior end portion toward the exterior end portion. The recess is tapered inwardly toward the central longitudinal along at least a portion of the depth of the recess.

In some embodiments, the body includes a face that is configured to oppose the suction cover when the suction cover nut is threadably connected within the access port of the fluid cylinder. The recess extends within the face and includes a sidewall that extends a length along the central longitudinal axis of the body. At least a portion of the length of the sidewall extends at non-parallel angle relative to the central longitudinal axis.

In one embodiment, the body includes a face that is configured to oppose the suction cover when the suction cover nut is threadably connected within the access port of the fluid cylinder. The recess extends within the face and includes a sidewall that extends a length from an edge of the face to a bottom surface of the recess at a non-parallel angle relative to the central longitudinal axis.

In some embodiments, the recess includes a sidewall having a length that spans a depth of the recess. The sidewall is tapered relative to the central longitudinal axis along an approximate entirety of the length of the sidewall.

In another embodiment, the recess extends into the body from a mouth of the recess to a bottom of the recess. The mouth of the recess has a greater width as compared to the bottom of the recess.

In yet another embodiment, the recess is tapered inwardly at an angle of between approximately 20° and approximately 30° relative to the central longitudinal axis of the body.

In some embodiments, at least a portion of the recess includes a conical shape.

In a second aspect, a suction cover assembly for a reciprocating pump includes a suction cover configured to be held at least partially within an access port of a fluid cylinder of the reciprocating pump. The suction cover includes a plug. The suction cover assembly includes a suction cover nut having a body configured to be at least partially received within the access port of the fluid cylinder. The body extends a length along a central longitudinal axis. The body includes a thread configured to threadably connect the suction cover nut to the fluid cylinder within the access port. The body includes a recess configured to receive the plug of the suction cover therein. The recess is tapered inwardly along the central longitudinal axis of the body.

In some embodiments, the suction cover extends a length along the central longitudinal axis. The plug of the suction cover is tapered inwardly along the central longitudinal axis.

In one embodiment, the plug of the suction cover is tapered inwardly along the central longitudinal axis. The plug of the suction cover and the recess of the suction cover nut are configured to mate together in physical contact such that axial forces acting during operation of the reciprocating pump are transferred radially outward relative to the central longitudinal axis.

In another embodiment, the recess of the suction cover nut and the plug of the suction cover include sidewalls that each extend at a non-parallel angle relative to the central longitudinal axis.

In some embodiments, the recess is tapered inwardly at an angle of between approximately 20° and approximately 30° relative to the central longitudinal axis, and the plug of the suction cover is tapered inwardly at an angle of between approximately 20° and approximately 30° relative to the central longitudinal axis.

In one embodiment, at least a portion of the recess of the suction cover nut includes a conical shape, and at least a portion of the plug of the suction cover includes a conical shape.

In some embodiments, the plug of the suction cover has a complementary shape relative to the recess of the suction cover nut.

In a third aspect, a reciprocating pump assembly includes a power end portion and a fluid end portion having a fluid cylinder that includes a pressure chamber and an access port. The access port extends along a central longitudinal axis. The access port includes an access port thread. The reciprocating pump assembly includes a suction cover assembly that includes a suction cover configured to be held at least partially within the access port of the fluid cylinder such that the suction cover extends a length along the central longitudinal axis. The suction cover includes a plug. The suction cover assembly includes a suction cover nut having a body configured to be at least partially received within the access port such that the body extends a length along the central longitudinal axis. The body includes a cover nut thread that is configured to be interlocked with the access port thread such that the suction cover nut is threadably connected to the fluid cylinder within the access port. The body includes a recess configured to receive the plug of the suction cover therein. The recess is tapered inwardly along the central longitudinal axis.

In one embodiment, the plug of the suction cover is tapered inwardly along the central longitudinal axis.

In some embodiments, the plug of the suction cover is tapered inwardly along the central longitudinal axis. The plug of the suction cover and the recess of the suction cover nut are configured to mate together in physical contact such that axial forces acting during operation of the reciprocating pump are transferred radially outward relative to the central longitudinal axis.

In some embodiments, the recess of the suction cover nut and the plug of the suction cover include sidewalls that each extend at a non-parallel angle relative to the central longitudinal axis.

Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of the inventions disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings facilitate an understanding of the various embodiments.

FIG. 1 is an elevational view of a reciprocating pump assembly according to an exemplary embodiment.

FIG. 2 is a cross-sectional view of a fluid cylinder assembly of the reciprocating pump shown in FIG. 1 according an exemplary embodiment.

FIG. 3 is a cross-sectional view of a portion of the fluid cylinder shown in FIG. 2 illustrating a suction cover assembly according to an exemplary embodiment.

FIG. 4 is a perspective view of a portion of the fluid cylinder shown in FIG. 2 illustrating another cross-sectional view of the suction cover assembly.

FIG. 5 illustrates the results of a finite element analysis (FEA) comparison of stress levels at the threads of a conventional suction cover assembly and the suction cover assembly embodiments described and/or illustrated herein.

Corresponding reference characters indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION

The embodiments described and/or illustrated herein provide a reciprocating pump assembly having a suction cover assembly that includes a tapered suction cover nut that transfers axial forces acting during operation of the reciprocating pump radially outward. Embodiments described and/or illustrated herein may provide a reciprocating pump assembly that may require less service, which may limit the downtime of the reciprocating pump assembly and/or reduce costs thereby improving the profitability of a well service or other operation utilizing the reciprocating pump assembly.

Referring to FIGS. 1 and 2, an illustrative embodiment of a reciprocating pump assembly 100 is presented. In FIGS. 1 and 2, the reciprocating pump assembly 100 includes a power end portion 102 and a fluid end portion 104 operably coupled thereto. The power end portion 102 includes a housing 106 in which a crankshaft (not shown) is disposed, the crankshaft is driven by an engine or motor (not shown). The fluid end portion 100 includes a fluid end block or fluid cylinder 108, which is connected to the housing 106 via a plurality of stay rods 110. In operation and as discussed in further detail below, the crankshaft reciprocates a plunger rod assembly 112 between the power end portion 102 and the fluid end portion 104. According to some embodiments, the reciprocating pump assembly 100 is freestanding on the ground, mounted to a trailer for towing between operational sites, mounted to a skid, loaded on a manifold, otherwise transported, and/or the like.

Referring now solely to FIG. 2, the plunger rod assembly 112 includes a plunger 114 extending through a bore 116 and into a pressure chamber 118 formed in the fluid cylinder 108. At least the bore 116, the pressure chamber 118, and the plunger 114 together may be characterized as a “plunger throw.” According to some embodiments, the reciprocating pump assembly 100 includes three plunger throws (i.e., a triplex pump assembly); however, in other embodiments, the reciprocating pump assembly 100 includes a greater or fewer number of plunger throws.

In the embodiment illustrated in FIG. 2, the fluid cylinder 108 includes fluid inlet and outlet passages 120 and 122, respectively, formed therein, which are generally coaxially disposed along a fluid passage axis 124. As described in greater detail below, fluid is adapted to flow through the fluid inlet and outlet passages 120 and 122, respectively, and along the fluid passage axis 124.

In the embodiment illustrated in FIG. 2, an inlet valve assembly 126 is disposed in the fluid inlet passage 120 and an outlet valve assembly 128 is disposed in the fluid outlet passage 122. In FIG. 2, the valve assemblies 126 and 128 are spring-loaded, which, as described in greater detail below, are actuated by at least a predetermined differential pressure across each of the valve assemblies 126 and 128. The inlet valve assembly 126 includes a valve seat 130 and a valve body 132 engaged therewith. The valve seat 130 includes a bore 134 that extends along a valve seat axis 136 that is coaxial with the fluid passage axis 124 when the inlet valve assembly 126 is disposed in the fluid inlet passage 120. The valve seat 130 further includes a shoulder 138, which in the exemplary embodiment is tapered (i.e., extends at an oblique angle relative to the valve seat axis 136). In other examples, the shoulder 138 of the valve seat 130 extends approximately perpendicular to the valve seat axis 136.

The valve body 132 includes a tail portion 140 and a head portion 142 that extends radially outward from the tail portion 140. The head portion 142 holds a seal 144 that sealingly engages at least a portion of the tapered shoulder 138 of the valve seat 130. In the exemplary embodiment, the head portion 142 is engaged and otherwise biased by a spring 146, which, as discussed in greater detail below, biases the valve body 132 to a closed position that prevents fluid flow through the inlet valve assembly 126.

In the embodiment illustrated in FIG. 2, the outlet valve assembly 128 is substantially similar to the inlet valve assembly 126 and therefore will not be described in further detail.

With reference to FIG. 2, operation of the reciprocating pump assembly 100 is discussed. In operation, the plunger 114 reciprocates within the bore 116 for movement into and out of the pressure chamber 118. That is, the plunger 114 moves back and forth horizontally, as viewed in FIG. 2, away from and towards the fluid passage axis 124 in response to rotation of the crankshaft (not shown) that is enclosed within the housing 106. Movement of the plunger 114 in the direction of arrow 148 away from the fluid passage axis 124 and out of the pressure chamber 118 will be referred to herein as the suction stroke of the plunger 114. As the plunger 114 moves along the suction stroke, the inlet valve assembly 126 is opened. More particularly, as the plunger 114 moves away from the fluid passage axis 124 in the direction of arrow 148, the pressure inside the pressure chamber 118 decreases, creating a differential pressure across the inlet valve assembly 126 and causing the valve body 132 to move upward in the direction of arrow 150, as viewed in FIG. 2, relative to the valve seat 130. As a result of the upward movement of the valve body 132, the spring 146 is compressed and the seal 144 separates from the tapered shoulder 138 of the valve seat 130 to the open position. Fluid entering through a fluid inlet passage 152 of the fluid cylinder 108 flows along the fluid passage axis 124 and through the inlet valve assembly 126, being drawn into the pressure chamber 118. To flow through the inlet valve assembly 126, the fluid flows through the bore 134 of the valve seat 130 and along the valve seat axis 136. During the fluid flow through the inlet valve assembly 126 and into the pressure chamber 118, the outlet valve assembly 128 is in a closed position wherein a seal 154 of a valve body 156 of the outlet valve assembly 128 is engaged with a tapered shoulder 158 of a valve seat 160 of the outlet valve assembly 128. Fluid continues to be drawn into the pressure chamber 118 until the plunger 114 is at the end of the suction stroke of the plunger 114, wherein the plunger 114 is at the farthest point from the fluid passage axis 124 of the range of motion of the plunger 114. At the end of the suction stroke of the plunger 114, the differential pressure across the inlet valve assembly 126 is such that the spring 146 of the inlet valve assembly 126 begins to decompress and extend, forcing the valve body 132 of the inlet valve assembly 126 to move downward in the direction of arrow 162, as viewed in FIG. 2. As a result, the inlet valve assembly 126 moves to and is otherwise placed in the closed position wherein the seal 144 of the valve body 132 is sealingly engaged with the tapered shoulder 138 of the valve seat 130.

Movement of the plunger 114 in the direction of arrow 164 toward the fluid passage axis 124 and into the pressure chamber 118 will be referred to herein as the discharge stroke of the plunger 114. As the plunger 114 moves along the discharge stroke into the pressure chamber 118, the pressure within the pressure chamber 118 increases. The pressure within the pressure chamber 118 increases until the differential pressure across the outlet valve assembly 128 exceeds a predetermined set point, at which point the outlet valve assembly 128 opens and permits fluid to flow out of the pressure chamber 118 along the fluid passage axis 124, being discharged through the outlet valve assembly 128. As the plunger 114 reaches the end of the discharge stroke, the inlet valve assembly 126 is positioned in the closed position wherein the seal 146 is sealingly engaged with the tapered shoulder 138 of the valve seat 130.

The fluid cylinder 108 of the fluid end portion 104 of the reciprocating pump assembly 100 includes an access port 166. The access port 166 is defined by an opening that extends through a body 168 of the fluid cylinder 108 to provide access to the pressure chamber 118 and thereby internal components of the fluid cylinder 108 (e.g., the inlet valve assembly 126, the outlet valve assembly 128, the plunger 114, etc.) for service (e.g., maintenance, replacement, etc.) thereof. The access port 166 of the fluid cylinder 108 is closed using a suction cover assembly 170 to seal the pressure chamber 118 of the fluid cylinder 108 at the access port 166. The suction cover assembly 170 may be selectively removed to enable access to the pressure chamber 118 and thereby the internal components of the fluid cylinder 108. In some circumstances (e.g., during field use of the reciprocating pump assembly 100, etc.), it may be desirable to access and thereby service the internal components of the fluid cylinder 108 relatively quickly, for example to limit the downtime of the reciprocating pump assembly 100 wherein the reciprocating pump assembly 100 is non-operational. The capability of servicing the reciprocating pump assembly 100 as quickly as possible and thereby limiting the downtime thereof may improve the profitability of a well service or other operation utilizing the reciprocating pump assembly 100. The reciprocating pump assembly 100 is not limited to frac pumps or the plunger rod pump shown herein. Rather, the embodiments disclosed herein may be used with any other type of pump that includes an access port.

The suction cover assembly 170 will now be described with reference to FIGS. 3 and 4. The access port 166 of the fluid cylinder 108 extends through the body 168 of the fluid cylinder 108 along a central longitudinal axis 172 and includes a cover segment 174 and a nut segment 176. The cover segment 174 includes a sealing surface 178 that is configured to be sealingly engaged by a seal 180 (not shown in FIG. 4) of the suction cover assembly 170. The nut segment 176 includes one or more threads 182 that are configured to interlock with one or more threads 184 of a suction cover nut 186 of the suction cover assembly 170. The threads 182 and 184 extend lengths along the central longitudinal axis 172 of the access port 166 and along a central longitudinal axis 188 of the suction cover assembly 170. The thread(s) 182 of the access port 166 may be referred to herein as an “access port thread”, while the thread(s) 184 of the suction cover nut 186 may be referred to herein as an “cover nut thread.”

The suction cover assembly 170 extends along the central longitudinal axis 188, which is coaxial with the central longitudinal axis 172 of the access port 166 when the suction cover assembly 170 is held within the access port 166 of the fluid cylinder 108. The suction cover assembly 170 includes a suction cover 190 and the suction cover nut 186. The suction cover 190 includes a body 192 that is held within the access port 166 of the fluid cylinder 108 by the suction cover nut 186. The body 192 of the suction cover 190 extends a length along the central longitudinal axis 188 and includes a base portion 194 and a head portion 196. As shown in FIGS. 3 and 4, the suction cover 190 is held within the access port 166 such that the base portion 194 is received within and extends along the cover segment 174 of the access port 166.

Although shown in FIG. 4 as having cylindrical shapes and/or circular shapes, the base portion 194 of the suction cover 190 and the cover segment 174 of the access port 166, and the seal 180 each may have any other shape that enables the suction cover 190 to at least partially seal the pressure chamber 118 at the access port 166 (e.g., a parallelepiped shape, a quadrilateral cross-sectional shape, a triangular cross-sectional shape, etc.).

In the exemplary embodiment illustrated herein, the head portion 196 of the suction cover 190 includes a flange 198 that extends radially outward relative to the base portion 194 of the suction cover 190. The flange 198 includes a seat surface 200 and the access port 166 of the fluid cylinder 108 includes a seat 202 that extends between the cover segment 174 and the nut segment 176 of the access port 166. As shown in FIGS. 3 and 4, the seat surface 200 of the flange 198 engages in physical contact with the seat 202 of the access port 166 of the fluid cylinder 108 when the suction cover 192 is held within the access port 166. The head portion 196 of the suction cover 190 includes a face 204 that faces the suction cover nut 186.

The head portion 196 of the suction cover 190 includes a plug 206 that extends outward from the base portion 194 along the central longitudinal axis 188. As will be described below, the plug 206 is configured to be received within a recess 208 of the suction cover nut 186 when the suction cover 190. The plug 206 will be described in more detail below.

The suction cover nut 186 includes a body 210 that is configured to hold the suction cover 190 in place within the access port 166. More particularly, the body 210 of the suction cover nut 186 includes the thread(s) 184, which are configured to interlock with the thread(s) 182 of the nut segment 176 of the access port 166 to threadably connect the suction cover nut 186 to the body 168 of the fluid cylinder 108. When threadably connected to the body 168 of the fluid cylinder 108 as shown in FIGS. 3 and 4, the suction cover nut 186 is positioned within the nut segment 176 of the access port 166 such that the suction cover nut 186 covers the suction cover 190 and thereby holds the suction cover 190 within the cover segment 174 of the access port 166. In the illustrated embodiment shown herein, the threads 182 and 184 of the access port 166 and the suction cover nut 186, respectively, are buttress threads having a pipe (i.e., hydraulic sealing) thread form (e.g., a 7.75 inch British Buttress Modified thread form, etc.) that is designed to provide a hydraulic seal and/or a greater unidirectional thread strength. But, any type of thread profile may be used, for example, any type of buttress thread form (e.g., a leadscrew thread profile, a Simple buttress thread form, an ANSI 45°/7° buttress thread form, a 45°/7° British buttress thread form, a 45°/5° buttress thread form, a 33°/3° German saw tooth buttress thread form, etc.), a square thread form, an Acme thread form, etc.

The body 210 of the suction cover nut 186 extends a length along the central longitudinal axis 190 from an exterior end portion 212 to an interior end portion 214. The interior end portion 214 of the suction cover nut 186 includes a face 216 that faces the suction cover 190. More particularly, the suction cover 190 is held by the fluid cylinder 108 (i.e., held within the access port 166 by the suction cover nut 186) such that the face 204 of the suction cover 190 opposes (i.e., faces) the face 216 of the suction cover nut 186. In other words, the faces 204 and 216 of the suction cover 190 and the suction cover nut 186, respectively, oppose each other (i.e., face toward each other).

The suction cover nut 186 includes an actuator 218 that enables the suction cover nut 186 to be rotated using a tool for threading the suction cover nut 186 into the access port 166 of the fluid cylinder 108 to thereby install the suction cover nut 186 and for unthreading the suction cover nut 186 to thereby remove the suction cover nut 186 from the access port 166. In the exemplary embodiment illustrated herein, the actuator 218 includes a socket 218 a configured to be engaged by a plug tool to rotate the suction cover nut 186, but any other type of actuator may be used that enables the suction cover nut 186 to be rotated using a tool, for example, one or more flats, any number or recesses that may be used by a spanner wrench to rotate the suction cover nut 186, a screw head for reception of a screw driver, etc.

As briefly described above, the body 210 of the suction cover nut 186 includes a recess 208 that is configured to receive the plug 206 of the suction cover 190 therein when the suction cover assembly 170 is installed within the access port 166. The recess 208 extends within the face 216 of the body 210 of the suction cover nut 186. More particularly, the recess 208 extends a depth D into the interior end portion 214 of the body 210 toward the exterior end portion 212. The depth D of the recess 208 extends into the body 210 from a mouth 220 of the recess 208 to a bottom 222 of the recess 208. As can be seen in FIGS. 3 and 4, the depth D of the recess 208 extends along the central longitudinal axis 188. The mouth 220 of the recess 208 is defined by an edge 224 of the face 216. The recess 208 includes a sidewall 226 that extends a length L along the central longitudinal axis 188 from the edge 224 to a bottom surface 228 that defines the bottom 222 of the recess 208. As shown in FIGS. 3 and 4, the length L of the sidewall 226 spans the depth D of the recess 208. The length L is not labeled in FIG. 4.

The recess 208 of the suction cover nut 186 is tapered inwardly along the central longitudinal axis 188. More particularly, the length L of the sidewall 226 extends at an angle α that is non-parallel relative to the central longitudinal axis 188 such that the recess 208 is tapered inwardly toward the central longitudinal axis 188. Accordingly, the mouth 220 of the recess 208 has a greater width as compared to the bottom 222 of the recess 208, as shown in FIGS. 3 and 4. In the illustrated embodiment of FIGS. 3 and 4, the angle α of the sidewall 226, and thus the amount of taper of the recess 208, is approximately 26°. But, the angle α of the sidewall 226 may be any angle that is non-parallel, for example approximately 45°, between approximately 20° and approximately 30°, between approximately 40° and approximately 50°, between approximately 10° and approximately 80°, between approximately 20° and approximately 70°, between approximately 30° and approximately 60°, between approximately 1° and approximately 89°, etc.

In the exemplary embodiment of FIGS. 3 and 4, the sidewall 226 is tapered (i.e., angled at the angle α) relative to the central longitudinal axis 188 along an approximate entirety of the length L of the sidewall 226. But, any amount of the length L of the sidewall 226, as well as any number of different locations along the length L of the sidewall 226, may be tapered (i.e., angled at the angle α) relative to the central longitudinal axis 188. In other words, in other examples, the recess 208 may be tapered inwardly toward the central longitudinal axis 188 along only one or more segments of the length L of the sidewall 226 (i.e., along only one or more portions of the depth D of the recess 208) such that one or more segments of the length L of the sidewall 226 do not taper inwardly toward (e.g., are angled approximately parallel relative to) the central longitudinal axis 188. It should be appreciated that such other examples include a recess 208 that has a stepped structure wherein one or more segments of the length L of the sidewall 226 are angled at the angle α and one or more segments of the length L of the sidewall 226 are angled approximately parallel relative to the central longitudinal axis 188.

Although shown in FIG. 4 as having a frustoconical shape, additionally or alternatively the recess 208 may include any other shape that enables the suction cover assembly 170 to function as described and/or illustrated herein (e.g., a pyramid shape, a pyramidal frustum shape, another conical shape that is not frustoconical, etc.).

As described above, the body 192 of the suction cover 190 includes a plug 206 that is configured to be received within the recess 208 of the suction cover nut 186. The plug 206 extends outward a length L₁ along the central longitudinal axis 188. The length L₁ of the plug 206 extends from a base 230 of the plug 206 to an end portion 232 of the plug 206. The base 230 of the plug 206 is defined by an edge 234 of the face 204 of the suction cover body 192. The plug 206 includes a sidewall 236 that extends a length L₂ along the central longitudinal axis 188 from the edge 234 to an end surface 238 that defines the end portion 232 of the plug 206. As shown in FIGS. 3 and 4, the length L₂ of the sidewall 236 spans the length L₁ of the plug 206. The length L₂ is not labeled in FIG. 4.

The plug 206 of the suction cover 190 is tapered inwardly along the central longitudinal axis 188. More particularly, the length L₂ of the sidewall 236 extends at an angle α₁ that is non-parallel relative to the central longitudinal axis 188 such that the plug 206 is tapered inwardly toward the central longitudinal axis 188. Accordingly, the base 230 of the plug 206 has a greater width as compared to the end portion 232 of the plug 206, as can be seen in FIGS. 3 and 4. The angle α₁ of the sidewall 236, and thus the amount of taper of the plug 206, is approximately 26° in the illustrated embodiment shown in FIGS. 3 and 4. But, the angle α₁ of the sidewall 236 may be any angle that is non-parallel, for example approximately 45°, between approximately 20° and approximately 30°, between approximately 40° and approximately 50°, between approximately 10° and approximately 80°, between approximately 20° and approximately 70°, between approximately 30° and approximately 60°, between approximately 1° and approximately 89°, etc.

In the exemplary embodiment of FIGS. 3 and 4, the sidewall 236 is tapered (i.e., angled at the angle α₁) relative to the central longitudinal axis 188 along an approximate entirety of the length L₂ of the sidewall 236. But, any amount of the length L₂ of the sidewall 236, as well as any number of different locations along the length L₂ of the sidewall 236, may be tapered (i.e., angled at the angle α₁) relative to the central longitudinal axis 188. In other words, in other examples, the plug 206 may be tapered inwardly toward the central longitudinal axis 188 along only one or more segments of the length L₂ of the sidewall 236 (i.e., along only one or more portions of the length L₁ of the plug 206) such that one or more segments of the length L₂ of the sidewall 236 do not taper inwardly toward (e.g., are angled approximately parallel relative to) the central longitudinal axis 188. It should be appreciated that such other examples include a plug 206 that has a stepped structure wherein one or more segments of the length L₂ of the sidewall 236 are angled at the angle α₁ and one or more segments of the length L₂ of the sidewall 236 are angled approximately parallel relative to the central longitudinal axis 188.

The plug 206 is not limited to the frustoconical shape shown herein. Rather, the plug 206 additionally or alternatively may include any other shape that enables the suction cover assembly 170 to function as described and/or illustrated herein (e.g., a pyramid shape, a pyramidal frustum shape, another conical shape that is not frustoconical, a cylindrical shape, etc.). For example, although the plug 206 of the suction cover 190 is shown herein with a complementary shape as compared to the recess 208 of the suction cover nut 186, in other embodiments the plug 206 does not have a complementary shape as compared to the recess 208 of the suction cover nut 186. In some examples, the majority or approximate entirety of the length L₂ of the sidewall 2236 of the plug 206 is not tapered inwardly toward the central longitudinal axis 188. For example, in some embodiments the majority or approximate entirety of the length L₂ of the sidewall 236 of the plug 206 extends approximately parallel to the central longitudinal axis 188 (i.e., such that the plug 206 has a cylindrical shape along the majority or approximate entirety of the length L₁ of the plug 206).

When the suction cover assembly 170 is installed within the access port 166 as shown in FIGS. 3 and 4, the plug 206 of the suction cover 190 is received within the recess 208 of the suction cover nut 186 such that the plug 206 and the recess 208 of the suction cover nut 186 mate together in physical contact. More particularly, the sidewall 236 of the plug 206 is engaged in physical contact with the sidewall 226 of the recess 208.

During cycling of the plunger 114 (FIG. 2) of the reciprocating pump assembly 100 between the higher-pressure discharge stroke and the lower pressure suction stroke, axial forces are exerted on the suction cover 190 that act approximately parallel to the central longitudinal axis 188. The taper of the sidewalls 226 and/or 236 and the engagement therebetween transfers (i.e., directs) the axial forces acting on the suction cover 190 radially outward relative to the central longitudinal axis 188 (e.g., in the directions of the arrows 240) through the suction cover nut 186 and the body 168 of the fluid cylinder 108. By directing the axial forces radially outward, the tapered suction cover nut 186 may reduce the amount of stress load concentrated at innermost thread portions 182 a and 184 a of the threads 182 and 184, respectively. The tapered suction cover nut 186 thereby may facilitate more evenly distributing the loads exerted on the threads 182 and 184 along the lengths of the threads 182 and 184 (e.g. a more even distribution along the full length of the threaded engagement of the threads 182 and 814 along the central longitudinal axes 172 and 188). The more even distribution of the stress loads exerted along the lengths of the threads 182 and 184 may increase the fatigue life of the threads 182 and 184.

The increase of the fatigue life of the threads 182 and 184 may extend the life of the suction cover nut 190 such that the suction cover assembly 170 may require less service, which may limit the downtime of the reciprocating pump assembly 100 and/or reduce costs thereby improving the profitability of a well service or other operation utilizing the reciprocating pump assembly 100.

The amount of taper of the sidewalls 226 and/or 236 (e.g., the value of the angles α and/or α₁), the amounts of the lengths of the sidewalls 226 and/or 236 that are tapered, the shapes of the plug 206 and/or the recess 208, the sizes of the plug 206 and/or the recess 208, and/or the like may be selected to: (1) reduce the stress loads concentrated at the innermost thread portions 182 a and 184 a of the respective threads 182 and 184 by a predetermined amount; (2) provide a predetermined distribution of loads across the length of the threads 182 and 184; and/or (3) increase the fatigue life of the threads 182 and 184 by a predetermined amount.

In some embodiments, the threads 182 and/or 184 are shot peened (e.g., double shot peened, etc.), heat treated, and/or subjected to one or more other hardening techniques to facilitate increasing the fatigue life of the threads 182 and/or 184.

EXAMPLES

A comparison of stress levels at the threads of a conventional suction cover assembly and the suction cover assembly embodiments described and/or illustrated herein (e.g., the suction cover assembly 170 shown in FIGS. 2-4) was performed using Finite Element Analysis (FEA). The FEA of various cross sections of the suction cover assemblies was performed using axisymmetric modeling, with the size of the mesh at thread and contact locations being approximately 0.02 inches. A second order quadrilateral element type was used with 90,683 nodes and 29,405 elements. The coefficient of friction between thread surfaces was defines as 0.1, while a coefficient of friction of 0.2 was defined between the suction cover and the suction cover nut and between the suction cover and the fluid cylinder.

FIG. 5 illustrates the results of the FEA comparison of stress levels at the threads of a conventional suction cover assembly and the suction cover assembly embodiments described and/or illustrated herein. As can be seen in the Table 5(a) and Graphs 5(b) and 5(c) of FIG. 5, the stress levels in the conventional suction cover assembly are higher as compared to the stress levels in the suction cover assembly embodiments described and/or illustrated herein.

The following clauses describe further aspects of the disclosure:

Clause Set A:

A1. A suction cover nut for a reciprocating pump, said suction cover nut comprising:

a body configured to be at least partially received within an access port of a fluid cylinder of the reciprocating pump, the body extending a length along a central longitudinal axis, the body comprising a thread configured to threadably connect the suction cover nut to the fluid cylinder within the access port, the thread extending along the central longitudinal axis of the body, the body comprising a recess configured to receive a suction cover of the reciprocating pump therein, wherein the recess is tapered inwardly along the central longitudinal axis of the body.

A2. The suction cover nut of clause A1, wherein the recess comprises a sidewall that is configured to transfer axial forces acting during operation of the reciprocating pump radially outward relative to the central longitudinal axis.

A3. The suction cover nut of clause A1, wherein the body extends the length along the central longitudinal axis from an exterior end portion to an interior end portion, the recess extending a depth into the interior end portion toward the exterior end portion, the recess being tapered inwardly toward the central longitudinal along at least a portion of the depth of the recess.

A4. The suction cover nut of clause A1, wherein the body comprises a face that is configured to oppose the suction cover when the suction cover nut is threadably connected within the access port of the fluid cylinder, the recess extending within the face and comprising a sidewall that extends a length along the central longitudinal axis of the body, wherein at least a portion of the length of the sidewall extends at a non-parallel angle relative to the central longitudinal axis.

A5. The suction cover nut of clause A1, wherein the body comprises a face that is configured to oppose the suction cover when the suction cover nut is threadably connected within the access port of the fluid cylinder, the recess extending within the face and comprising a sidewall that extends a length from an edge of the face to a bottom surface of the recess at a non-parallel angle relative to the central longitudinal axis.

A6. The suction cover nut of clause A1, wherein the recess comprises a sidewall having a length that spans a depth of the recess, the sidewall being tapered relative to the central longitudinal axis along an approximate entirety of the length of the sidewall.

A7. The suction cover nut of clause A1, wherein the recess extends into the body from a mouth of the recess to a bottom of the recess, the mouth of the recess having a greater width as compared to the bottom of the recess.

A8. The suction cover nut of clause A1, wherein the recess is tapered inwardly at an angle of between approximately 20° and approximately 30° relative to the central longitudinal axis of the body.

A9. The suction cover nut of clause A1, wherein at least a portion of the recess includes a conical shape.

Clause Set B:

B1. A suction cover assembly for a reciprocating pump, said suction cover assembly comprising:

a suction cover configured to be held at least partially within an access port of a fluid cylinder of the reciprocating pump, the suction cover comprising a plug; and

a suction cover nut comprising a body configured to be at least partially received within the access port of the fluid cylinder, the body extending a length along a central longitudinal axis, the body comprising a thread configured to threadably connect the suction cover nut to the fluid cylinder within the access port, the body comprising a recess configured to receive the plug of the suction cover therein, wherein the recess is tapered inwardly along the central longitudinal axis of the body.

B2. The suction cover assembly of clause B1, wherein the suction cover extends a length along the central longitudinal axis, the plug of the suction cover being tapered inwardly along the central longitudinal axis.

B3. The suction cover assembly of clause B 1, wherein the plug of the suction cover is tapered inwardly along the central longitudinal axis, the plug of the suction cover and the recess of the suction cover nut being configured to mate together in physical contact such that axial forces acting during operation of the reciprocating pump are transferred radially outward relative to the central longitudinal axis.

B4. The suction cover assembly of clause B1, wherein the recess of the suction cover nut and the plug of the suction cover comprise sidewalls that each extend at a non-parallel angle relative to the central longitudinal axis.

B5. The suction cover assembly of clause B1, wherein the recess is tapered inwardly at an angle of between approximately 20° and approximately 30° relative to the central longitudinal axis, the plug of the suction cover being tapered inwardly at an angle of between approximately 20° and approximately 30° relative to the central longitudinal axis.

B6. The suction cover assembly of clause B1, wherein at least a portion of the recess of the suction cover nut includes a conical shape, and at least a portion of the plug of the suction cover includes a conical shape.

B7. The suction cover assembly of clause B 1, wherein the plug of the suction cover has a complementary shape relative to the recess of the suction cover nut.

Clause Set C:

C1. A pump assembly, comprising:

a power end portion;

a fluid end portion having a fluid cylinder that includes a pressure chamber and an access port, the access port extending along a central longitudinal axis, the access port comprising an access port thread; and

a suction cover assembly comprising:

-   -   a suction cover configured to be held at least partially within         the access port of the fluid cylinder such that the suction         cover extends a length along the central longitudinal axis, the         suction cover comprising a plug;     -   a suction cover nut comprising a body configured to be at least         partially received within the access port such that the body         extends a length along the central longitudinal axis, the body         having a cover nut thread that is configured to be interlocked         with the access port thread such that the suction cover nut is         threadably connected to the fluid cylinder within the access         port, the body comprising a recess configured to receive the         plug of the suction cover therein, wherein the recess is tapered         inwardly along the central longitudinal axis.

C2. The pump assembly of clause C1, wherein the plug of the suction cover is tapered inwardly along the central longitudinal axis.

C3. The pump assembly of clause C1, wherein the plug of the suction cover is tapered inwardly along the central longitudinal axis, the plug of the suction cover and the recess of the suction cover nut being configured to mate together in physical contact such that axial forces acting during operation of the reciprocating pump are transferred radially outward relative to the central longitudinal axis.

C4. The pump assembly of clause C1, wherein the recess of the suction cover nut and the plug of the suction cover comprise sidewalls that each extend at a non-parallel angle relative to the central longitudinal axis.

It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. Furthermore, invention(s) have been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Further, each independent feature or component of any given assembly may constitute an additional embodiment. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as “clockwise” and “counterclockwise”, “left” and right”, “front” and “rear”, “above” and “below” and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

When introducing elements of aspects of the disclosure or the examples thereof, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. For example, in this specification, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised”, “comprises”, “having”, “has”, “includes”, and “including” where they appear. The term “exemplary” is intended to mean “an example of.” The phrase “one or more of the following: A, B, and C” means “at least one of A and/or at least one of B and/or at least one of C.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112(f), unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.

Although the terms “step” and/or “block” may be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly described. The order of execution or performance of the operations in examples of the disclosure illustrated and described herein is not essential, unless otherwise specified. The operations may be performed in any order, unless otherwise specified, and examples of the disclosure may include additional or fewer operations than those disclosed herein. It is therefore contemplated that executing or performing a particular operation before, contemporaneously with, or after another operation is within the scope of aspects of the disclosure.

Having described aspects of the disclosure in detail, it will be apparent that modifications and variations are possible without departing from the scope of aspects of the disclosure as defined in the appended claims. As various changes could be made in the above constructions, products, and methods without departing from the scope of aspects of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 

What is claimed is:
 1. A suction cover nut for a reciprocating pump, said suction cover nut comprising: a body configured to be at least partially received within an access port of a fluid cylinder of the reciprocating pump, the body extending a length along a central longitudinal axis, the body comprising a thread configured to threadably connect the suction cover nut to the fluid cylinder within the access port, the thread extending along the central longitudinal axis of the body, the body comprising a recess configured to receive a suction cover of the reciprocating pump therein, wherein the recess is tapered inwardly along the central longitudinal axis of the body.
 2. The suction cover nut of claim 1, wherein the recess comprises a sidewall that is configured to transfer axial forces acting during operation of the reciprocating pump radially outward relative to the central longitudinal axis.
 3. The suction cover nut of claim 1, wherein the body extends the length along the central longitudinal axis from an exterior end portion to an interior end portion, the recess extending a depth into the interior end portion toward the exterior end portion, the recess being tapered inwardly toward the central longitudinal along at least a portion of the depth of the recess.
 4. The suction cover nut of claim 1, wherein the body comprises a face that is configured to oppose the suction cover when the suction cover nut is threadably connected within the access port of the fluid cylinder, the recess extending within the face and comprising a sidewall that extends a length along the central longitudinal axis of the body, wherein at least a portion of the length of the sidewall extends at a non-parallel angle relative to the central longitudinal axis.
 5. The suction cover nut of claim 1, wherein the body comprises a face that is configured to oppose the suction cover when the suction cover nut is threadably connected within the access port of the fluid cylinder, the recess extending within the face and comprising a sidewall that extends a length from an edge of the face to a bottom surface of the recess at a non-parallel angle relative to the central longitudinal axis.
 6. The suction cover nut of claim 1, wherein the recess comprises a sidewall having a length that spans a depth of the recess, the sidewall being tapered relative to the central longitudinal axis along an approximate entirety of the length of the sidewall.
 7. The suction cover nut of claim 1, wherein the recess extends into the body from a mouth of the recess to a bottom of the recess, the mouth of the recess having a greater width as compared to the bottom of the recess.
 8. The suction cover nut of claim 1, wherein the recess is tapered inwardly at an angle of between approximately 20° and approximately 30° relative to the central longitudinal axis of the body.
 9. The suction cover nut of claim 1, wherein at least a portion of the recess includes a conical shape.
 10. A suction cover assembly for a reciprocating pump, said suction cover assembly comprising: a suction cover configured to be held at least partially within an access port of a fluid cylinder of the reciprocating pump, the suction cover comprising a plug; and a suction cover nut comprising a body configured to be at least partially received within the access port of the fluid cylinder, the body extending a length along a central longitudinal axis, the body comprising a thread configured to threadably connect the suction cover nut to the fluid cylinder within the access port, the body comprising a recess configured to receive the plug of the suction cover therein, wherein the recess is tapered inwardly along the central longitudinal axis of the body.
 11. The suction cover assembly of claim 10, wherein the suction cover extends a length along the central longitudinal axis, the plug of the suction cover being tapered inwardly along the central longitudinal axis.
 12. The suction cover assembly of claim 10, wherein the plug of the suction cover is tapered inwardly along the central longitudinal axis, the plug of the suction cover and the recess of the suction cover nut being configured to mate together in physical contact such that axial forces acting during operation of the reciprocating pump are transferred radially outward relative to the central longitudinal axis.
 13. The suction cover assembly of claim 10, wherein the recess of the suction cover nut and the plug of the suction cover comprise sidewalls that each extend at a non-parallel angle relative to the central longitudinal axis.
 14. The suction cover assembly of claim 10, wherein the recess is tapered inwardly at an angle of between approximately 20° and approximately 30° relative to the central longitudinal axis, the plug of the suction cover being tapered inwardly at an angle of between approximately 20° and approximately 30° relative to the central longitudinal axis.
 15. The suction cover assembly of claim 10, wherein at least a portion of the recess of the suction cover nut includes a conical shape, and at least a portion of the plug of the suction cover includes a conical shape.
 16. The suction cover assembly of claim 10, wherein the plug of the suction cover has a complementary shape relative to the recess of the suction cover nut.
 17. A pump assembly, comprising: a power end portion; a fluid end portion having a fluid cylinder that includes a pressure chamber and an access port, the access port extending along a central longitudinal axis, the access port comprising an access port thread; and a suction cover assembly comprising: a suction cover configured to be held at least partially within the access port of the fluid cylinder such that the suction cover extends a length along the central longitudinal axis, the suction cover comprising a plug; a suction cover nut comprising a body configured to be at least partially received within the access port such that the body extends a length along the central longitudinal axis, the body having a cover nut thread that is configured to be interlocked with the access port thread such that the suction cover nut is threadably connected to the fluid cylinder within the access port, the body comprising a recess configured to receive the plug of the suction cover therein, wherein the recess is tapered inwardly along the central longitudinal axis.
 18. The pump assembly of claim 17, wherein the plug of the suction cover is tapered inwardly along the central longitudinal axis.
 19. The pump assembly of claim 17, wherein the plug of the suction cover is tapered inwardly along the central longitudinal axis, the plug of the suction cover and the recess of the suction cover nut being configured to mate together in physical contact such that axial forces acting during operation of the reciprocating pump are transferred radially outward relative to the central longitudinal axis.
 20. The pump assembly of claim 17, wherein the recess of the suction cover nut and the plug of the suction cover comprise sidewalls that each extend at a non-parallel angle relative to the central longitudinal axis. 